"Can't imagine what you'd need missile-proof glass and four thousand pounds of body armor for around here."

―One of the two men Bella meets at the gas station, commenting on Bella's Mercedes Guardian[src]

The Mercedes Guardian is Bella's "before" car in Breaking Dawn. It is a present from Edward to replace her Chevy truck.
It is described as sleek and shiny, said to be missile-proof with four thousand pounds of body armor and supposed to be released only in Europe and extremely expensive. One of the two men Bella meets at the gas station comments that you could attack it with a flamethrower or run a tanker over it and still not damage it.

Edward makes it clear to Bella that the car is only borrowed, and that he will return it once she's been changed. Bella realizes this is one of Edward's (overprotective) attempts to keep her safe from any danger.

"This car highlights the inherent differences in how Edward views Bella. Bella is content with her seat belt-lacking Chevy, while Edward puts her in a car generally reserved for land mine-avoiding oil sheiks, sparing no effort, or expense, to protect her in every way possible."